1. Field of the Invention
The present invention relates to an image recording apparatus and an image recording method, and more specifically to an image recording apparatus and an image recording method using a digital line-exposing device for exposure of a photosensitive material.
2. Description of the Related Art
Conventionally, when a PLZT (lead lanthanum zirconate titanate) head is used for exposure of a photosensitive material, there is a problem that an intensity of irradiation light from each shutter portion (optical outputting portion) of the PLZT head changes depending on an ON/OFF frequency of the shutter portion. In order to solve this problem, generally, an optical sensor is run widthwise of the PLZT head to perform scanning for measurement of the intensity of the irradiation light from each shutter portion, and correction to the intensity of the irradiation light (known as a shading correction) is performed periodically.
For example, according to a proposal in Japanese Patent Laid-Open No. 6-347923 made by the applicant of the present invention, when a timer has accumulated a predetermined amount of time, the photosensitive material is removed from an exposing portion, and the optical sensor is run to make the scan for measuring the irradiation light intensity of the PLZT head. Then, based on the measurements, a ratio of the measured irradiation light intensity to a norm value is obtained for each of the shutter portions of the PLZT head as a measured data, and an inverse of the measured data is obtained as a correction data. This correction data is multiplied by an amount of exposure, and a resulting product is used as a basis for determining a corrected exposure time.
However, according to the above proposal, although the irradiation light intensity can be corrected, an accurate detection and calculation of the irradiation light intensity must be performed for each shutter portion, spending about 20 minutes. This causes another problem of decreased processing capacity of the image recording apparatus due to a loss of time. Especially, when the proposal disclosed in Japanese Patent Laid-Open 6-347923 is used, the decrease in the processing capacity becomes more significant if the timer is set to a shorter accumulation time.